Layout the Porch Rail Pickets

After priming and painting the western red cedar boards for the porch rail, I sawed the 8 foot boards 1″ longer than needed to allow for a margin of error during final fitting. Next I laid the 2″ x 2″ x 36″ pickets on 5″ centers to ensure everything would turn out the way I expected. A 2×4 block is perfect for spacing the pickets on 5″ centers with a 3-1/2″ gap between pickets to satisfy the building code. Recall that a 4″ sphere cannot pass between the pickets per the building code.

2×6 Porch Rail Construction

I stacked the boards upside down on the sawhorses to illustrate how the top rail and pickets will be assembled. Nothing is nailed or screwed together here:

2×6 Porch Rail Concept (Upside down)

This photo shows how the porch rails are assembled with exterior screws:

The subrail is fastened to the edge of side rail with a Grip-Rite 3″ stainless steel screw.

The 2×6 top rail is fastened to the 2×4 subrail with a 2-1/2″ DECK MATE EVERCOTE exterior screw.

The screw length is important so as not to over-penetrate the boards. Corrosion resistant or stainless steel screws are a must for exterior applications and required per the building code.

Why use screws instead of nails? Because screws won’t back out over time as the boards expand and shrink with seasonal temperature changes.

2×6 and 2×4 Porch Rail Assembly with Wood Screws

Porch Subrail and Side Rail Assembly

I could have built the deck rail in place on the front porch, but I’m working at night in the workshop to make progress. The porch rail is a little over 6 feet long, so carrying it outside to the front porch won’t be a problem.

The subrail is laid face down on the edge of the 2×4 subrail and fastened with 3″ stainless steel screws on 8″ centers starting about 2″ inches from the end of the board. Take care to drive the 3″ screw straight down so you don’t punch through the face of the side rail. The best way to align the subrail over the side rail is to double it with another 2×4 as shown.

Build a Porch Rail: Fasten the 2×4 Subrail to the 2×4 Side Rail

Here’s the 2×4 subrail after fastening the 2×4 side rail with screws on 8″ centers. Note the unpainted 2×4 board used as support while I was driving the screws.

Build a Porch Rail: 2×4 Subrail and Side Rail Assembly

The screws are sealed with a dab of white GE Silicone II Paintable Silicone caulk – I like this brand because it’s “30 minute paint ready” and silicone doesn’t shrink or crack and stays permanently flexible. The purpose of the caulk is to seal the wood around the screw.

Build a Porch Rail: Caulk the Wood Screws

View of the assembled and caulked subrail and side rail (left side of photo). The 2×6 top porch rail on the right will be attached next.

Build a Deck or Porch Rail: Assembled and Caulked Subrail and Side Rail

Install the 2×6 Porch Top Rail

The 2×6 top rail will be fastened to the 2×4 subrail with 2-1/2″ DECK MATE EVERCOTE exterior wood screws:

Build a Porch or Deck Rail: 2×6 Top Rail to 2×4 Subrail Assembly

I set the screws on 8″ centers starting 6″ from the end of the board as shown, placing two screws side-by-side at both ends and the center to eliminate any possible wobble. The screws are set flush with the face of the 2×6 board so there’s no bump.

Build a 2×6 Porch or Deck Rail

The screw heads given a dab of caulk and smoothed with 2″ putty knife to make the screws almost invisible. After the caulk dries, the top rail is given another coat of Sherwin-Williams Duration® paint. Always paint exterior caulk because it’s slightly tacky and will collect dirt/dust if left unpainted.

Caulk the 2×6 Porch Rail Wood Screws

Here’s the assembled and painted 2×6 porch rail and stack of 2×2 pickets: